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Neuromuscular monitoring – time to change our approach?

February-March 2017

2017 is now well underway Trump continues to dominate both media and informal peer conversations. Politics has never been so distracting and Trumps directives do make it hard to concentrate on more everyday tasks. There is an increasing underlying sense of concern being expressed by many regarding the policies and overall direction. We know the impact politics has on health professionals who work across borders and we will keep a close eye on developments in this area.

For me, one of the greatest rewards but also biggest challenges I have found in my role of NZSA President, is keeping up with and coming to grips with the various issues as they arise. Not infrequently a few do go past the keeper or get caught in slips. A recent example is the review of PS18, the professional document stipulating monitoring standards and in particular those relating to neuromuscular monitoring.  The Safety and Quality Committee of ANZCA is responsible for overseeing professional documents. Each document is regularly reviewed, changes suggested and a year’s cool down or review period is then allocated. The review period for PS18 finished earlier this month. I communicated with you just prior to this requesting you to complete a survey in relation to PS18. Thank you for partaking in this. We had 262 responses which is an almost 50% response rate and the results are as follows:


Q1 How often do you use a nerve stimulator to monitor neuromuscular function?

Always 18.3%
Often 35.8%
Sometimes 27.8%
Rarely 16.4%
Never 1.5%


Q2 When monitoring neuromuscular function, I use:

A nerve stimulator and assess response by either visually or tactile (qualitative) 70.7%
Assess quantitatively (e.g. accelerometer)    29.2%

Q3 At all sites that I practise, quantitative neuromuscular function monitor is immediately available to me:

Always 30.6%
Often 26.3%
Sometimes 19.4%
Rarely 16.1%
Never 7.6%


Q4 In which of the following situations would you routinely use a neuromuscular function monitor?

Following suxamethonium 25.2%
Following an intubating dose of nondepoloaring blocker 42.6%
Following repeated dosages of non-depolariser 76%
If at risk patient factors suggest (renal or liver impairment, aminoglycoside use, short surgical time) 80.8%
Other (please specify) 23.1%

I was pleasantly surprised at the frequency of monitoring in general but in particular the availability and use of quantitative monitors.

Rightly or wrongly I was concerned that the new wording implied that routine monitoring with a quantitative monitor was now the standard of care.

Quantitative neuromuscular function monitoring must be available for every patient in whom neuromuscular blockade has been induced and should be used whenever the anaesthetist is considering extubation following the use of non-depolarising neuromuscular blockade.   

  1. Firstly, it is a change management issue. Unless the wider body of practitioners believes that the standard is relevant they will not engage with it. This then risks a disconnect between the standard setters and grassroot practitioners; not a situation we want. It is therefore important that as a collective body we buy into this approach and believe that such monitoring is warranted. All the literature would suggest we need to lift our game from where it currently is and many jurisdictions are now mandating a higher standard of practice. For example, from the AAGBI: A peripheral nerve stimulator must be used whenever neuromuscular blocking drugs are given. A quantitative peripheral nerve stimulator is recommended.” Interestingly, Barash in his top 20 articles places at number 13 an article discussing anaesthetic mortality in 1954; without curare mortality of 1:2, 100 and with 1:370.
  2. Value proposition: To borrow a trendy term from Michael Porter, or as some more cynical may say, a ‘Porterism.’ To bring an outfit the size of Waikato Hospital up to speed would cost in the order of $40K with a further 25% of that cost each subsequent year. (The cost of one back operation says you. Now that could lead to an interesting value proposition discussion). Provided we are adding value to the perioperative process that is well spent money but if we are not then we are in essence irresponsible. I personally am not 100% sure that mandating quantitative monitoring on all patients that receive non-depolarisers is adding value.
  3. The survey shows that the current practice is that most anaesthetists do not routinely monitor neuromuscular function. If they do, most do so in selected high risk situations and monitor qualitatively. We have assumed that this approach in conjunction with the intermediate duration drugs currently available, along with routine use of reversal, has for the most part worked well. The current literature and recent webAIRS data supports this impression. As a result, our approach to neuromuscular function has become pragmatic and empiric rather than scientific and standardised.
    However, as in all aspects of life the bar is slowly but inevitably rising; traditionally a train of four recovery of (TOF) >0.7 was accepted but the standard now is >0.9.  And this I think is the guts of the issue, the problem with qualitative monitoring is that clinically it is difficult to distinguish between a TOF fade of 0.4 and 0.9. This is referred to as “the blind zone of paralysis.” So clinically the new standard is of little relevance because without quantitative monitors we cannot detect it. However, a TOF of 0.7 is associated with significant paralysis. Although this may not manifest in the PACU it may be associated with impaired swallowing and subtle hypoventilation leading to aspiration, atelectasis and perhaps pneumonia. However, as we increasingly push the boundaries with older and sicker patients these (subtle) factors become increasingly important. So, perhaps it is time to change our approach to neuromuscular monitoring.

This subject remains very topical as illustrated by the number of recent articles. I have listed the ones below that I have referred to. I confess I have learnt more than I thought I would by reading these. The first one gives an excellent overview, the second talks in detail about using a nerve stimulator and the third looks at the good, bad and the ugly in regard to traditional reversal. For example: “These data suggest that empiric, routine full dose (neostigmine 0.07mg/kg) reversal of light or minimal neuromuscular block is not advised.”

Once again, thank you for your feedback on this topic. And as always, “may the force be with you.”

David

References:
Lein CA, Kopman AF. Current recommendations for monitoring depth of neuromuscular blockade. Current Opinions in Anestheiol 2014, 27:616-622

Thilen SR, Bhananker SM. Qualitative Neuromuscular Monitoring: How to Optimize the use of a Peripheral Nerve Stimulator to Reduce the Risk of Residual Neuromuscular Blockade

Brull SJ, Kopman AF. Current Status of Neuromuscular Reversal and

Monitoring: Challenges and Opportunities. Anesthesiology 2017; 126:173–90

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